Reusing soil (tomatoes) - informational observations

tapla (mid-MI z5b-6a)September 9, 2012

Last fall, when I went to empty my 18 gallon containers of 5:1:1 soil into the compost pile I found that over 3-4 years of use, the sun had destroyed the structural integrity of the rim of the tubs I was using to the degree that when I tried to lift the tubs the handles & rims were breaking. My option then, was to leave the tubs in place with the soil exposed to the weather over the winter in an attempt to get another year out of the set-up, or replace the tubs & soil. I felt confident in my ability to gauge water needs, so decided to turn it into something of an experiment.

In late May, I pulled the weeds in the tubs & used a trowel to turn the old soil over, stripped the bottom leaves off the sets and planted the sets deep. As the plants grew, I stripped the lower leaves and back-filled the containers with fresh 5:1:1 until they were filled, the old soil being 5:1:1 that was a year old at planting time. I ended up adding about 1/4 of the container's total volume as new soil.

The results weren't awful, but there were notable differences between last years results in fresh soil and this years in the soil that underwent a growth cycle of use and a winter's worth of composting. I would estimate this years plants to be about half the size in terms of o/a vegetative mass, and the yields to be about 2/3 of what I had last year. I'm currently getting some typical dieback of just the lower foliage, but the vines continue to bloom & set fruit. If I had no basis for comparison, I think I'd be perfectly happy with both the condition/appearance of the foliage as well as the yields. In fact, since I have more tomatoes than I need or can eat from the 6 plants I have, I'd call my decision a good one, even though it's clear I left a fair amount of potential lying on the table.

To be fair, it's also possible that the intense heat we suffered for several weeks in late Jul through mid-Aug had some impact on the outcome, but I tend to think not so much because the foliage never seemed to suffer. Still, I'm prevented from making any sweeping conclusions based on how things went down. I just thought there might be some interest, even though all I have is a strong suspicion the difference was primarily related to the reduction in the % of air the soil was capable of holding, in spite even of the care I took in watering.

Interesting experiment. I did one of my own. Last year I used a classic 511 mix. This year I used new pine bark, BUT instead if peat, I used recycled (last years) 511, and increased it by an additional part for more water retention. So my mix was something like 5:2 with only a little perlite. The results were that my tomatoes grew much better than last year, and I'm not sure why. Maybe there was more nutrients in the recycled 511. My plants were (and still are) HUGE, and I only used 5 gallon buckets this year and last year I used bigger containers, 5-15 gallon. I would estimate 1000 tomatoes from my Black Cherry, and 20 over a pound from my Brandywine with a whole new flush almost ripe. Actually the Brandywine is in a 10 gal container, but the rest in 5 gal.

I would have to agree with your assessment, Al. I find that when I don't completely dig out and either remix and replace most of the medium, or use fresh medium, in my larger containers, I don't get the results I'd like to see. I put it all on the medium's ability to drain properly and allow for a decent exchange of fresh oxygen and gases. I can usually get decent results for a couple of seasons without too much hassle, but not beyond that.

As to the breakdown of the containers, themselves... I suppose there isn't much that lasts forever, but it sure seems like nothing is made the way it used to be! :-)

Weather is hard on some types of plastics, wood containers, and some of the fake terra cotta looking pots... that's for sure!

Nice job, Edweather... good looking plants! I admit to being totally spoiled, myself, through all the information I've gleaned from Al's writings. I've learned that simple science and physics plays a huge role when it comes to container growing and mediums. I'll never go back to the industry standard!

Al, thanks for posting up your observations and reflections.
This year, my Sun Gold container tomato (15-gallon) seems to be larger than ever.
I'm using fresh 5-1-1, of course, so that's no surprise. Lime, generous Osmocote up front,
a couple treatments of Foliage Pro, and I haven't done much other than water every 3 - 4 days.

With my hot peppers in containers, I haven't gotten the results that I did last year,
but I think that is mostly due to the fact that I didn't start my seeds until the third week of March!
Thus, my plants are quite a bit smaller in stature, and I expect that production will be lower as well.

One other variable, however, is the particular 5-1-1 that I used this year.
This year, I used one full part of peat-based potting mix (Foxfarm's Ocean Forest product).
Last year, I used one half part of potting mix and one half part of Turface for binding and
moisture retention. Anyhow, given the difference in seed-starting dates, I won't be able to
solidify any conclusions - but I will be returning to the Turface mix...and starting seeds earlier...
next season.

I was going to do a decent veggie planting this past season, but the goofy weather threw me off, and I decided that it wasn't worth the effort of getting too huge, what with all the other work I have to do... so, not so much in the area of veggies... but I grew a large Hippeastrum bulb and some Hymenocallis in large pots outside, and one nice Plumeria. And then I have the red Japanese Maple that desperately needs a root trim and re-potting.

Between the dry and the heat, and the stronger sun this season... or, at least it sure seemed so... a lot of my plants ended up with burnt leaves and didn't do as well as they could have.

But that Hippeastrum grew HUGE, and the Hymenocallis did exceedingly well! It took the Plumeria some time to leaf out, but it's doing good. The poor red maple burned horridly, and I can see that it got more cicada damage than I had thought from the previous year.

All in all, a strange year... but having the tools to cope (knowledge) sure helped me. :-)

I plant my tomatoes in pots and then at the end of the season spread the tomato pot soil over my perennial bed. That way I improve the heavy clay soil in our perennial garden and avoid wintering over viruses that could harm next years tomatoes. My dad was a farmer and he always advocated rotating your crops. Since our yard does not have a lot of sun, I cannot rotate my tomatoes so I have decided to rotate the dirt!